Understanding Normality (N)
* Normality is a concentration unit that measures the number of equivalents of a solute per liter of solution.
* An equivalent is the amount of a substance that can react with or replace one mole of hydrogen ions (H⁺) or hydroxide ions (OH⁻).
Na₂CO₃ and Equivalents
* Sodium carbonate (Na₂CO₃) is a base. When it dissolves in water, it reacts with water to produce carbonate ions (CO₃²⁻), which can accept two hydrogen ions (H⁺).
* Therefore, one mole of Na₂CO₃ is equivalent to two equivalents (because it can accept two moles of H⁺).
Calculating the Mass Needed
1. Molar mass of Na₂CO₃: 105.99 g/mol
2. Equivalents per mole: 2 equivalents/mol (as explained above)
3. Desired normality: 0.02 N
4. Volume of solution: 1 L
Calculations:
* Grams of Na₂CO₃ needed: (0.02 N) * (1 L) * (105.99 g/mol) / (2 equivalents/mol) = 1.06 g
Conclusion
Adding 1.06 g of Na₂CO₃ to 1 liter of water produces a 0.02 N solution because this mass provides the correct number of equivalents of Na₂CO₃ to achieve the desired normality.
